This invention relates generally to drive axles and more particularly to drive axles that include a lubricant cooling system.
U.S. Pat. No. 1,247,276 granted to William B. Hurlburt Nov. 20, 1917 discloses a self oiling rear axle wherein a gear wheel throws oil from a sump up into a shell. The shell has a close fit with a worm wheel that drives the gear wheel. This worm wheel forces the oil into a duct that feeds the oil to inner and outer bearings through a network of interconnected ducts. The oil then returns to the sump. The patent does not discuss oil temperature nor mention oil cooling.
U.S. Pat. No. 1,950,034 granted to William A. Mulford et al Mar. 6, 1934 discloses a rear axle that has oil cooling provisions. This rear axle has a ring gear that carries scoops that dip into oil in the bottom of the housing and throw the oil up into the interior of a worm housing. The worm housing includes external fins for cooling the oil that is thrown into the worm housing. The worm gear then pumps the oil through oil passages to the worm bearings. The oil then circulates through the worm bearings and returns to the bottom of the housing.
U.S. Pat. No. 4,352,301 granted to Edward Fleury Oct. 5, 1982 discloses an axle assembly that also has an oil cooling system. This oil cooling system includes a small lubrication pump that picks up oil from a reservoir in a gear housing and pumps the oil through an external filter to cool and clean the oil. The filtered oil is returned by pipes that extend through the axle tubes. The returning oil flows outwardly along the axle tubes so that oil is sprayed onto the ends of the half shafts and delivered to the shaft end bearings via holes. The oil then returns to the axle tubes via reduction gear assemblies and drains back to the gear housing by gravity. The patent states that the oil is cooled due to the circulation through the external filter and also indicates that an external oil cooler may be added if the cooling provided by the external filter is insufficient.
German Patent Application DE 40 23 354 applied for by Mercedes-Benz Aktiengelesschaft and published Jan. 30, 1992 discloses a drive axle assembly that is equipped with an oil circulation system. In this system, a ring gear splashes oil from a reservoir up into an elevated internal chamber in the differential housing portion of an axle housing. The oil accumulates in the elevated chamber and then flows by gravity to axle bearings and hub gears at the outboard ends of the axle housing via internal conduits. The oil then flows back to the reservoir through the central passages of the axle housing that surround the axle shafts. The continuous exchange of oil reduces the operating temperature of the hub gears at the outboard ends of the axle housing.
None of the above patent documents disclose a drive axle assembly with a lubricant cooling system that is simple, efficient and economical.